Clarify warning, update links (mainly https)

doc/latex/biblatex/biblatex.tex

@@ -55,8 +55,8 @@
 \newcommand*{\biber}{\sty{biber}\xspace}
 \newcommand*{\biblatex}{\sty{biblatex}\xspace}
 \newcommand*{\biblatexml}{\sty{biblatexml}\xspace}
-\newcommand*{\biblatexhome}{http://sourceforge.net/projects/biblatex/}
-\newcommand*{\biblatexctan}{http://ctan.org/pkg/biblatex/}
+\newcommand*{\biblatexhome}{https://sourceforge.net/projects/biblatex/}
+\newcommand*{\biblatexctan}{https://ctan.org/pkg/biblatex/}
 
 \titlepage{%
   title={The \biblatex Package},
@@ -173,7 +173,7 @@
 \section{Introduction}
 \label{int}
 
-This document is a systematic reference manual for the \biblatex package. Look at the sample documents which come with \biblatex to get a first impression.\fnurl{\biblatexctan doc/examples}
+This document is a systematic reference manual for the \biblatex package. Look at the sample documents which come with \biblatex to get a first impression.\fnurl{https://ctan.org/tex-archive/macros/latex/contrib/biblatex/doc/examples}
 For a quick start guide, browse \secref{int:abt, bib:typ, bib:fld, bib:use, use:opt, use:xbx, use:bib, use:cit, use:use}.
 
 \subsection[About]{About \biblatex}
@@ -183,12 +183,12 @@ \section{Introduction}
 
 \subsection{License}
 
-Copyright \textcopyright\ 2006--2012 Philipp Lehman, 2012--2017 Philip Kime, Audrey Boruvka, Joseph Wright, 2018-- Philip Kime and Moritz Wemheuer. Permission is granted to copy, distribute and\slash or modify this software under  the terms of the \lppl, version~1.3.\fnurl{http://www.latex-project.org/lppl.txt}
+Copyright \textcopyright\ 2006--2012 Philipp Lehman, 2012--2017 Philip Kime, Audrey Boruvka, Joseph Wright, 2018-- Philip Kime and Moritz Wemheuer. Permission is granted to copy, distribute and\slash or modify this software under  the terms of the \lppl, version~1.3.\fnurl{https://www.latex-project.org/lppl.txt}
 
 \subsection{Feedback}
 \label{int:feb}
 
-Please use the \biblatex project page on GitHub to report bugs and submit feature requests.\fnurl{http://github.com/plk/biblatex} Before making a feature request, please ensure that you have thoroughly studied this manual. If you do not want to report a bug or request a feature but are simply in need of assistance, you might want to consider posting your question on the \texttt{comp.text.tex} newsgroup or \tex-\latex Stack Exchange.\fnurl{http://tex.stackexchange.com/questions/tagged/biblatex}
+Please use the \biblatex project page on GitHub to report bugs and submit feature requests.\fnurl{https://github.com/plk/biblatex} Before making a feature request, please ensure that you have thoroughly studied this manual. If you do not want to report a bug or request a feature but are simply in need of assistance, you might want to consider posting your question on the \texttt{comp.text.tex} newsgroup or \tex-\latex Stack Exchange.\fnurl{https://tex.stackexchange.com/questions/tagged/biblatex}
 
 \subsection{Acknowledgements}
 
@@ -243,19 +243,21 @@ \subsubsection{Requirements}
 The \biblatex package requires \etex. \tex distributions have been providing \etex binaries for quite some time, the popular distributions use them by default these days. The \biblatex package checks if it is running under \etex. Simply try compiling your documents as you usually do, the chances are that it just works. If you get an error message, try compiling the document with \bin{elatex} instead of \bin{latex} or \bin{pdfelatex} instead of \bin{pdflatex}, respectively.
 
 \item[\biber]
-\biber is the backend of \biblatex used to transfer data from source files to the \latex code. \biber comes with TeX Live and is also available from SourceForge.\fnurl{http://biblatex-biber.sourceforge.net/}. \biber uses the \texttt{btparse} C library for \bibtex format file parsing which aimed to be compatible with \bibtex's parsing rules but also aimed at correcting some of the common problems. For details, see the manual page for the Perl \texttt{Text::BibTeX} module\fnurl{http://search.cpan.org/~ambs/Text-BibTeX}.
+\biber is the backend of \biblatex used to transfer data from source files to the \latex code. \biber comes with TeX Live and is also available from SourceForge.\fnurl{https://biblatex-biber.sourceforge.net/}. \biber uses the \texttt{btparse} C library for \bibtex format file parsing which aimed to be compatible with \bibtex's parsing rules but also aimed at correcting some of the common problems. For details, see the manual page for the Perl \texttt{Text::BibTeX} module\fnurl{https://metacpan.org/release/Text-BibTeX}.
 
 \item[etoolbox]
-This \latex package, which is loaded automatically, provides generic programming facilities required by \biblatex. It is available from \acr{CTAN}.\fnurl{http://ctan.org/pkg/etoolbox}
+This \latex package, which is loaded automatically, provides generic programming facilities required by \biblatex. It is available from \acr{CTAN}.\fnurl{https://ctan.org/pkg/etoolbox}
 
 \item[kvoptions]
-This \latex package, which is also loaded automatically, is used for internal option handling. It is available with the \sty{oberdiek} package bundle from \acr{CTAN}.\fnurl{http://ctan.org/pkg/kvoptions}
+This \latex package, which is also loaded automatically, is used for internal option handling. It is available from \acr{CTAN}.\fnurl{https://ctan.org/pkg/kvoptions}
 
 \item[logreq]
-This \latex package, which is also loaded automatically, provides a frontend for writing machine-readable messages to an auxiliary log file. It is available from \acr{CTAN}.\fnurl{http://ctan.org/pkg/logreq/}
+This \latex package, which is also loaded automatically, provides a frontend for writing machine-readable messages to an auxiliary log file. It is available from \acr{CTAN}.\fnurl{https://ctan.org/pkg/logreq/}
 
 \item[pdftexcmds]
-This \latex package, which is loaded automatically, implements \pdftex primitives for \luatex, it also offers a unified interface for these primitives across engines. It is available from \acr{CTAN}.\fnurl{http://ctan.org/pkg/pdftexcmds/}
+This \latex package, which is loaded automatically, implements \pdftex primitives for \luatex, it also offers a unified interface for these primitives across engines. It is available from \acr{CTAN}.\fnurl{https://ctan.org/pkg/pdftexcmds/}
+
+\biblatex uses \sty{pdftexcmds} to access the MD5 hash primitives, so version~0.27 (2018/01/30) or above is strongly recommended.
 
 \end{marglist}
 
@@ -274,10 +276,10 @@ \subsubsection{Recommended Packages}
 \biblatex has only limited support for \sty{polyglossia} versions prior to~v1.45. If \sty{polyglossia} is used, it should be updated to version~1.45 (2019/10/27) or above.
 
 \item[csquotes]
-If this package is available, \biblatex will use its language sensitive quotation facilities to enclose certain titles in quotation marks. If not, \biblatex uses quotes suitable for American English as a fallback. When writing in a language other than American English, loading \sty{csquotes} is strongly recommended.\fnurl{http://ctan.org/pkg/csquotes/}
+If this package is available, \biblatex will use its language sensitive quotation facilities to enclose certain titles in quotation marks. If not, \biblatex uses quotes suitable for American English as a fallback. When writing in a language other than American English, loading \sty{csquotes} is strongly recommended.\fnurl{https://ctan.org/pkg/csquotes/}
 
 \item[xpatch]
-The \sty{xpatch} package extends the patching commands of \sty{etoolbox} to \biblatex bibliography macros, drivers and formatting directives.\fnurl{http://ctan.org/pkg/xpatch/}
+The \sty{xpatch} package extends the patching commands of \sty{etoolbox} to \biblatex bibliography macros, drivers and formatting directives.\fnurl{https://ctan.org/pkg/xpatch/}
 
 \end{marglist}
 
@@ -1847,7 +1849,7 @@ \subsubsection{Cross-referencing}
 \subsubsection{Sorting and Encoding Issues}
 \label{bib:cav:enc}
 
-\biber handles Ascii, 8-bit encodings such as Latin\,1, and \utf. It features true Unicode support and is capable of reencoding the \file{bib} data on the fly in a robust way. For sorting, \biber uses a Perl implementation of the Unicode Collation Algorithm (\acr{UCA}), as outlined in Unicode Technical Standard \#10.\fnurl{http://unicode.org/reports/tr10/} Collation tailoring based on the Unicode Common Locale Data Repository (\acr{CLDR}) is also supported.\fnurl{http://cldr.unicode.org/}
+\biber handles Ascii, 8-bit encodings such as Latin\,1, and \utf. It features true Unicode support and is capable of reencoding the \file{bib} data on the fly in a robust way. For sorting, \biber uses a Perl implementation of the Unicode Collation Algorithm (\acr{UCA}), as outlined in Unicode Technical Standard \#10.\fnurl{https://unicode.org/reports/tr10/} Collation tailoring based on the Unicode Common Locale Data Repository (\acr{CLDR}) is also supported.\fnurl{http://cldr.unicode.org/}
 
 Supporting Unicode implies much more than handling \utf input. Unicode is a complex standard covering more than its most well-known parts, the Unicode character encoding and transport encodings such as \utf. It also standardizes aspects such as string collation, which is required for language-sensitive sorting. For example, by using the Unicode Collation Algorithm, \biber can handle the character <ß> without any manual intervention. All you need to do to get localised sorting is specify the locale:
 

tex/latex/biblatex/biblatex.sty

@@ -584,13 +584,17 @@
 \ifundef\pdf@mdfivesum
   {\let\blx@mdfivesum\@firstofone
    \blx@warning@noline{Command '\string\pdf@mdfivesum' undefined.\MessageBreak
-     'labelprefix' may not be able to accept all input}}
+     'labelprefix' may not be able to accept all input.\MessageBreak
+     The command is available (via 'pdftexcmds')\MessageBreak
+     in recent versions of pdfTeX, LuaTeX and XeTeX}}
   {\let\blx@mdfivesum\pdf@mdfivesum}
 
 
 \ifundef\pdf@filemdfivesum
   {\blx@warning@noline{Command '\string\pdf@filemdfivesum' undefined.\MessageBreak
-     Biber rerun detection may not work as expected}%#
+     Biber rerun detection may not work as expected.\MessageBreak
+     The command is available (via 'pdftexcmds')\MessageBreak
+     in recent versions of pdfTeX, LuaTeX and XeTeX}%
    \let\blx@generate@bbl@mdfivesum@found\relax
    \let\blx@generate@bbl@mdfivesum@notfound\relax
    \let\aux@read@bbl@mdfivesum\@gobble